Good, but a few points
I love the model design. It's a really nice weapon, and I think that this could be a really excellent 3D piece, but for a few things.
(a) It's blurry. That's weird in 3D.
(b) All the circular pieces need more faces, particularly the sight scope.
(c) The reflections in the metal are too strong, and a real material that's bumpy like that wouldn't have the clear reflections that you have.
(d) BEVEL. You did some, apparently by hand (woot), but it's not enough.
You clearly worked really hard on this, and it shows in a lot of details. I'm just offering simple improvements, not detracting from the value of the piece. Good stuff!